Understanding Earth's Structure, Tectonics, and Geological Processes

Earth's Structure and Composition

a) False, the mantle has a semi-plastic behavior (asthenosphere). b) True. c) False, the mantle lies between the crust and the core, approximately 2900km in depth. d) False, the lithosphere is a solid layer where magma currents originate. e) False, the temperature inside the nucleus is about 4500 º C.

The lithosphere is a solid surface layer that surrounds the Earth. It has an average thickness of 100km and consists of the solid crust and the upper mantle layer (residual mantle), which lies above the asthenosphere.

Tectonic Plates and Their Movement

A tectonic plate is a piece of the lithosphere that can be pushed and moved by magma currents beneath it. This movement produces earthquakes at constructive plate boundaries (where plates separate due to magma pressure) and destructive plate boundaries (due to the sudden sinking of one plate).

Volcanoes: Formation and Types

Volcanoes are structures that form around openings where magma rises. There are two main types of volcanoes:

• Vent volcanoes: Formed when magma flows through a single opening.
• Fissure volcanoes: Formed when magma emerges through cracks.

Earthquakes: Causes and Effects

Earthquakes are vibrations of the lithosphere caused by sudden displacement of a section of the lithosphere relative to another. They occur at plate boundaries: constructive boundaries (where plates separate due to magma pressure) and destructive boundaries (where plates collide, causing one to sink).

a) False, the place where the rupture occurs is called the hypocenter or focus of the earthquake. b) True. c) False, surface waves are the most destructive. d) False, there are no reliable prediction methods. e) True.

Faults and Folds: Geological Formations

Faults are fractures where there is relative displacement between two fault blocks. Rocks are subjected to geological forces produced by the movement of tectonic plates. The difference between normal and reverse faults is that normal faults originate from tensional forces, causing the block above the fault plane to sink, while reverse faults are caused by compressional forces, causing the block above the fault plane to rise.

a) False, a fold axis forming an angle of 50° with the ground is inclined. b) True. c) The dip is the angle formed by the flank with the horizontal ground. d) False, compressional geological forces can cause folding. e) True.

Magma and Igneous Rocks

a) Magma is a fluid formed by molten rock that contains a large amount of gases. b) Igneous rocks are formed by the cooling and solidification of magma. c) They differ in that granular texture is made up of crystals of a visible size, porphyritic texture is formed by large crystals immersed in a mass of microcrystals, and vitreous texture is not composed of crystals.

a) True. b) True. c) False, igneous rocks can not be disintegrated. d) False, an igneous rock is formed by the fusion and solidification of rocks. e) True

Geothermal Gradient and Magma Currents

The geothermal gradient of the Earth's crust increases at a rate of 3°C per 100 meters. Magma currents are common in fused rocks amounting to the lithosphere, which is divided and moves slowly beneath them, eventually returning to the area of the asthenosphere from which they originated. The difference between oceanic and mixed plates is that oceanic plates are formed by the thin oceanic crust of basaltic rocks (found in the ocean), while mixed plates include both continents and the seafloor.

a) 5 b) 2 c) 4 d) 1 e) 3

1) Crater 2) Lava flows 3) Volcanic cone 4) Volcanic chimney 5) Volcanic plume 6) Layers of pyroclasts 7) Magma chamber

Geological Hazards: Earthquakes and Tsunamis

Heavy soil vibrations that can bring down buildings, bridges... thrust of hillsides that can cause the burial of the nearest residential areas, strong series of sea waves or tsunamis move at great speed and can devastate coastal areas.

1) Block 2) Hypocenter 3) Fault plane or rupture 4) Epicenter 5) Seismic waves